Position sensing system and method for an inspection handling system

ABSTRACT

A carrier tape drive used in conjunction with a pick and place module. The drive advances carrier tape to a desired position in two steps. The first step includes substantially stopping a carrier tape compartment short of a loading position, and the second step includes moving the compartment into the loading position.

RELATED APPLICATIONS

This application is a national stage filing under 35 U.S.C. §371 ofinternational application PCT/US98/14618, filed Jul. 15, 1998 and whichdesignates the United States. The aforementioned internationalapplication claims the benefit under 35 U.S.C. §119 of co-pendingprovisional patent applications 60/052,698, filed Jul. 16, 1997 and60/076,702, filed Mar. 4, 1998.

FIELD OF THE INVENTION

The invention relates to a position sensing system, and moreparticularly, to a position sensing system for use in a taper module ofan inspection and handling system for devices such as semiconductors.

BACKGROUND OF THE INVENTION

Some devices, such as integrated circuit chips, need to be preciselyfabricated. Accordingly, inspection of such devices is necessary toascertain whether the devices meet exacting acceptance standards. Thedevices to be inspected are often provided in compartmented trays whichhave multiple rows and columns of pockets in which the devices aretransported.

An inspection and handling system is utilized to inspect such devices.Trays of devices are transported through various stages of theinspection and handling system including laser scanning, inversion,camera scanning and individual placement at a final destination so thatdevices meeting the exacting acceptance standards are separated fromthose devices which do not meet such standards.

One final destination of devices that meet the acceptance standards iscarrier tape. Typically, carrier tape is an elongate tape which includespockets that are arranged in series. The pockets are typically shaped tobe complementary to the dimensions of the devices that are to be housedtherein. An instrument such as a vacuum operated precisor of a pick-andplace system can transport a device from a tray into a pocket of thecarrier tape. Once devices are individually placed into the pockets ofthe carrier tape, a cover tape is often applied and the carrier tapewith devices housed in the sealed pockets can be wound onto a reel andconveniently transported to another destination, such as where thedevices will be put into final use.

Pick and place systems are generally capable of motion in one direction(transverse to the direction of movement of trays through the inspectionand handling system) and have limited, if any, movement in a directionperpendicular to that motion (parallel to the direction of movement ofthe trays). Therefore, the carrier tape needs to be incrementally movedby a drive system so that the pick and place system can place devicesinto successive pockets of the carrier tape. It is therefore necessaryto determine the location of individual pockets of the carrier tape withrespect to the pick and place system. Typically, the carrier tapeincludes sprocket holes that run the length of the carrier tape on oneor both sides of the pockets. The sprocket holes are utilized todetermine the position of a pocket relative to the pick and placesystem.

In some inspection and handling systems, problems may occur if thecarrier tape is not consistently advanced by the proper distanceequivalent to the length of one pocket. Traditionally, the beginning ofa pocket is determined by forwarding the carrier tape by a fixeddistance, and assuming that the carrier tape moved forward the distanceprogrammed. Use of a sensor may also be employed to detect the number ofsprocket holes passed as the carrier tape is advanced. In such systems,the drive system assumes that the point to which the carrier tape isforwarded is the correct starting point of the pocket.

Specifically, in some systems, simply advancing the carrier tape by aset distance, or counting the number of sprocket holes passed, may notbe sufficiently accurate in determining the position of a pocket. Jitteror slipping of the carrier tape can occur. In the case of slipping, thecarrier tape may not be advanced the amount the drive system isprogrammed to advance. In the case of jitter, the carrier tape may movebackward, thereby counting a sprocket hole twice. Accordingly, errorsmay incur in determining the location of a pocket.

An object of this invention is to achieve accurate and reliableplacement of a carrier tape, or the like, relative to a pick and placeassembly or the like.

SUMMARY OF THE INVENTION

For the achievement of those and other objects, this invention proposesto achieve the desired placement of the carrier tape in two steps. Afirst step positions one of the compartments in the tape in the vicinityof but not at the final placement position, and the second subsequentstep moves the compartment into placement position.

More specifically, the carrier tape has a plurality of compartments of asize to receive one semiconductor device. The compartments are seriallyspaced along the longitudinal axis of the tape and the tape alsoincludes a plurality of sprocket holes serially spaced along a linewhich is parallel to said longitudinal axis. The distance betweencompartments corresponds to a predetermined number of sprocket holesand, in the first step, the tape is advanced a distance corresponding toless than that predetermined number of sprocket holes. In the secondstep, the tape is advanced the remaining number of said sprocket holes.Preferably, the first step is equal to one less than the distancebetween the predetermined number of sprocket holes and the second stepis equal to the distance to the last sprocket hole.

Preferably, this invention also contemplates transporting the tape byengaging the tape surfaces and not the sprocket holes, and it includesthe capability of inspecting for the presence of a device in the tapecompartment and proper positioning of the device in the compartment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of a tape positioning system embodying thisinvention;

FIG. 2 is a plan view, in schematic form, of a carrier tape with thepositioning sensor;

FIG. 3 is a side view of the drive roller assembly;

FIG. 4 is an end view, partly in section of the drive roller assembly ofFIG. 3;

FIG. 5 is a plan view of the tape positioning system of FIG. 1;

FIG. 6 is a side view of the device sensing mechanism;

FIG. 7 is a plan view of the mechanism of FIG. 6;

FIG. 8 is a plan view of a sensor assembly;

FIG. 9 is a side view of a sensor assembly;

FIG. 10 is a schematic diagram of the tape positioning sensing system;and

FIG. 11 is a timing diagram of the tape position sensing system.

Before one embodiment of the invention is explained in detail, it is tobe understood that the invention is not limited in its application tothe details of construction and the arrangement of components or stepsset forth in the following description or illustrated in the drawings.The invention is capable of other embodiments and of being practiced orbeing carried out in various other ways. Also, it is to be understoodthat the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Before describing the tape positioning system, a type of carrier tapepackaging system will be described.

With reference to the drawings, the tape positioning system 100 is shownin association with a precisor 200 of a typical pick and place (PNP)system. The PNP system will only be shown schematically to illustrateits relationship with the tape positioning system.

The relationship of the PNP system to the overall inspection andhandling system and a taper system or module can be as set forth inco-pending U.S. application Ser. No. 09/142,338, filed Sep. 27, 1999 andentitled “Inspection Handler Apparatus and Method” and assigned to theassignee of this application. If details of those relationships arenecessary, reliance is placed on that co-pending application.

The tape system includes a carrier tape drive 102 that draws carriertape from a supply reel assembly 104 and conveys the carrier tapethrough a device placement station 106, several inspection stations, acover tape placement station 108, and a heat seal station 110 to anoutfeed reel assembly 112. Further, it includes a frame 114 whereon themajor assemblies are mounted and a control system 116 for coordinatingthe various operations of the tape positioning system.

In general terms, carrier tape 120 is drawn from reel 104 by thecombination of friction roller 122, driven by drive 102, and frictionroller 124, driven by drive 126. The carrier tape travels throughplacement station 106, is engaged with covering tape 128 from reel 130,then passes through heat seal station 110 where the cover tape is sealedto the carrier tape, and goes to its destination on reel 112.

FIG. 2 depicts one of several types of carrier tape 12 used in thesemiconductor industry and adaptable for use in this system. Rectangularshaped device pockets 20 are spaced uniformly along the longitudinalaxis of the carrier tape 12. The pockets are dimensioned to fit with aparticular semiconductor device and each pocket includes a central testhole 22. The distance between test holes 22 is commonly referred to asthe pitch 24 of the carrier tape.

The carrier tape also has a series of uniformly spaced sprocket holes 14provided along one or both edges 16 and 18 of the carrier tape. Thesprocket holes are a means for driving the carrier tape. Typically, thesealed carrier tape provided by the tape system is unwound by thesemiconductor device user using the sprocket holes 14. To reduce therisk of damage to the sprocket holes, this taper positioning system doesnot use the sprocket holes 14 to drive the tape 102 through the tapermodule.

In lieu of sprockets, this tape system utilizes soft friction rollers atboth the main drive, roller 122, and the take-up drive, roller 124, todrive and guide the carrier tape through the various stations to thecarrier tape 102 as the carrier tape is driven by the soft roller.

Referring to FIG. 3, a main drive roller 122 is mounted between a pairof mounting blocks 132 near the left ends of the guide rails 146, 148.The main drive roller comprises a core 134 mounted onto a drive shaft136 and has an outer layer 138 of urethane material.

A pinch roller 139 is supported beneath roller 122 and preferably is ofthe same general construction as roller 122. A pneumatic assembly 140 isconnected to the mount for roller 139 and is operative to move theroller 139 up or down to vary the pressure exerted on the carrier tapeas it passes between the rollers.

Drive shaft 136 is driven by stepper motor 102 through a pulley system142.

Elongated guide rails 146, 148 (See FIG. 5) extend from the drive roller122 through roller 124. The carrier tape 120 is shown entering theroller 122 and exiting roller 124 but not between for clarity ofillustration of the intervening parts. The edges of the carrier tape arecaused to travel snugly over the guide rails 146, 148 as it is conveyedthrough the device placement and inspection stations. The center hole 22of the individual pockets of the carrier tape is maintained positioneddirectly above the centerline of the rail gap 144.

The precisor 200 (shown in dotted lines in FIG. 5) from the PNP moduleis positionable overhead of the guide rails to the right of the maindrive roller 122 and over the rail gap 144. The precisor places devicesinto individual pockets 20 of the carrier tape. The precisor, except forthe device which actually engages the circuit devices by movingvertically, is capable of movement in only one direction. That directionis illustrated by arrow 201 in FIG. 5.

A tape position sensor assembly 32 is mounted adjacent the front guiderail 146 and will be described more completely hereafter.

Referring again to FIGS. 5 and 6, a part hold down assembly 150 isdisposed to the right of the tape position sensor assembly 32 and thedevice placement station 106. Referring to FIGS. 6 and 7, the hold downassembly 150 includes a left pivot arm 152 and a right pivot arm 154,and a hold down bar 156 that is fastened across both pivot arms 152,154. The pivot arms 152, 154 extend over the rear guide rail 148 andsupport the hold down bar 156 directly over the rail gap 144.

The pivot arms 152, 154 are pivotably connected to a mounting block 158by a bushing 160. The part hold down assembly is biased such that thearms 152, 154 pivot downward and the hold down bar 156 rests down ontothe carrier tape. A leading or left end of the hold down bar 156 may bebeveled so as to guard against the hold down bar catching on the passingcarrier tape. The hold down bar 156 typically rides over the carriertape pockets as the carrier tape is conveyed forward. Pressure appliedby the hold down bar on the carrier tape helps to keep devices in thecarrier pockets.

Further, a proximiter probe 162 is vertically mounted to the left pivotarm 152 at a location directly above the rear guide rail 148. The probeend extends downwardly through the left pivot arm 152 and is set to facethe top surface of the front guide rail 148. The proximiter probe sensesvertical displacement of the left pivot arm 152. When an unseated deviceprotrudes outward of a pocket 20, the hold down bar 156 and the leftpivot arm 152 are displaced upwardly as the carrier tape passesunderneath, thereby alarming the probe. In this event, the carrier tapedrive may be prompted to reverse index the carrier pocket so that theunseated device is returned to the device placement station. At thatpoint, the precisor may pick and discard the unseated device, andreplenish the carrier pocket with another device.

A missing part photo sensor assembly 165 of conventional construction ispreferably the through-beam type is disposed to the right of the holddown bar assembly 150 and directly overhead of the rail gap 144 andincludes a photo sensor 163 located above rail gap 144 and emitter coneassembly (not shown) supported below the rail gap 144.

When a carrier tape pocket 20 is moved past the photo sensor without adevice therein, the exposed center hole allows the through beam to bepicked up by the emitter cone. Accordingly, the carrier tape drive isprompted to move the carrier tape in the reverse direction until theempty pocket is vertically aligned with the device placement station. Atthis point, the precisor is prompted to place a device in the emptycarrier pocket.

After passing through those testing stations, the carrier tape pocket isready to be sealed. In the cover tape placement station 108, cover tapeis directed over the pockets. The cover tape placement station 108includes a supply reel 130 that is mounted overhead of the guide rails146, 148.

Below the supply reel shaft, an idler roller 167 and a conventionalvacuum manifold 164 are separately mounted to the support place. Thecover tape travels from the supply reel 130, underneath the idler roller167 and over the vacuum manifold 164 before engaging the cover taperoller 166. The vacuum manifold applies a constant drag on the covertape between the vacuum manifold 164 and the cover tape roller 166. Thecover tape is brought into engagement with the carrier tape under roller166 and covers the pockets 20 in the carrier tape.

After the cover tape is applied over the carrier tape, the carrier tapeis conveyed to the heat seal station 110. The heat seal mechanism isconventional and thus will not be described in detail.

The roller 124 is a take up roller. In the preferred embodiment of theinvention, the main drive roller assembly 102 has the primaryresponsibility for pushing the carrier tape, while the take-up driveroller assembly 124 maintains tension on the carrier tape. The take-updrive roller assembly is disposed across the guide rails 146, 148 tonear to the right end of the module frame, feeding sealed carrier tapeto the outfeed reel assembly 112.

The construction and arrangement of the take up roller 124 and itsassociated parts is the same as that at main drive roller 122, includingthe pressure roller and pneumatic assembly to vary pressure between themain roller and the pressure roller, and a stepper motor to drive roller124. For that reason, it will not be described in detail. The relativespeeds of rotation of the rollers 122 and 124 are controlled in aconventional manner to maintain the proper tension on the carrier tapeas it passes through the various operations.

Referring to the drawings, FIG. 2 illustrates a tape position sensingsystem 10 which operates to determine the position of carrier tape 102.

The carrier tape 12 has a series of uniformly spaced sprocket holes 14provided along one or both edges 16 and 18 of the carrier tape 12. Thesprocket holes 14 can be used as a means for driving the carrier tape12. A plurality of pockets, such as pocket 20, are positionedsequentially along the carrier tape 12, and are dimensioned to becomplementary to devices that are to be housed therein.

After devices have been housed in the pockets 20 of the carrier tape 12,the ultimate user of the devices typically will utilize the sprocketholes 14 as a means by which to move the carrier tape 12. To reduce oreliminate the risk of damage to the sprocket holes 14, it is preferablethat the inspection and handling system does not utilize the sprocketholes 14 as part of the drive system. Preferably, a friction drive isutilized to move the carrier tape 12 through the taper module of theinspection and handling system. The friction drive will be describedhereinafter.

In the present invention, to determine the beginning of a pocket 20 ofthe carrier tape 12 and thus the proper position of the tape andcompartment, a known fixed distance to advance the carrier tape 12(corresponding to a set number of sprocket holes) is preprogrammed suchas in an encoder. This fixed distance lies between the last sprockethole (n) and the second to last sprocket hole (n−1) adjacent to the endof pocket 20, where n is the number of sprocket holes corresponding tothe spacing between pockets 20.

A pair of conventional photo sensors P1 and P2 detect the passing of theserial sprocket holes 14 as the carrier tape 12 is advanced by the drivesystem.

In the embodiment shown in FIG. 1, P1 and P2 are 2 mm apart and a pocketlength is the distance between four of the sprocket holes 14. The numberof sprocket holes 14 passed by the photo sensors P1 and P2 is counted bythe encoder. Preferably, the carrier tape 12 is advanced rapidly(“jumped”) by the drive system the distance of the jump zone, n−1sprocket holes. The carrier tape 12 is then slowly advanced (“crept”) bythe drive system until the edge of the last sprocket hole 14 (n) isreached. The photo sensors P1 and P2 are used to determine when the edgeof the n^(th) sprocket hole 14 is reached to determine the end of thecurrent pocket 20, and accordingly, the beginning of the next pocket 20.

With reference to FIG. 2, the sprocket holes are spaced on centers 2, inthe preferred embodiment 4 mm. There is a distance 4 between the leadingand trailing edges of adjacent sprockets, that is leading and trailingrelative to the direction of travel of the tape illustrated by arrow 6.In the preferred embodiment, the spacing between is equal to or lessthan the distance 4. Specifically in this embodiment the spacing 4equals 2 mm.

With reference to FIG. 10, a circuit schematic of the tape positionsensing system 10 is illustrated. The circuit processes the informationreceived from the photo sensors P1 and P2 resulting from the detectionof the passing of sprocket holes 14. Specifically, the photo sensors P1and P2 are electrically connected to transistors Q1 and Q2. Each sourceof transistors Q1 and Q2 is electrically connected to a conventional SRflip-flop 30, through Schottky diodes D1 and D2. The source oftransistor Q1 is electrically connected to the “S” input of SR flip-flop30, and the source of transistor Q2 is electrically connected to the “R”input of SR flip-flop 30. Each drain of transistors Q1 and Q2 isgrounded.

When the first or leading photo sensors P1 detects a sprocket hole 14, asignal is sent to transistor Q1 and to flip-flop 30, setting theflip-flop 30. When the second or trailing photo sensors P2 detects asprocket hole 14, a signal is sent to transistor Q2 and to flip-flop 30,resetting the flip-flop. As flip flop 30 is set and reset, the “Q”output of the flip flop is fed to the encoder which increments asprocket hole counter. The sprocket holes being advanced are counted inthis manner.

Turning now to FIG. 8, the photo sensors P1 and P2 are shown. A sensorassembly 32 is mounted adjacent to a front guide rail 146 of the tapermodule. The sensor assembly 32 supports the photo sensors P1 and P2.Each photo sensor P1 and P2 typically includes a beam element 36 and 38,and pick-up elements 40 and 42 opposed to elements 36 and 38,respectively. One of the pick up elements 42 is visible in FIG. 8. Whenthe carrier tape 12 is caused to move linearly along the rail guide 146,the series of sprocket holes 14 pass directly between the beam elements36 and 38 and the pick-up elements 40 and 42.

The sensor assembly 32 is mounted horizontally on an elongated supportblock 44 that extends substantially into a slot on the front guide rail146. As illustrated, both photo sensors P1 and P2 are mounted on thesame support block 44. However, it is contemplated that each sensor P1and P2 may be supported separately and accordingly, the position of eachphoto sensor P1 and P2 may be adjusted separately. The support block 44is mounted to a bracket via a ball slide 46. By operating a rotatabledial 48, the support block 44 may be secured to or loosened from thebracket. A micrometer 50 is mounted on the left of the support block 44and engages the support block 44 with a ball tip 46. Through adjustmentof the micrometer 50, the lateral position of the sensor assembly 32 inthe slot of the front guide rail 34 may be fine tuned.

With reference to FIG. 11, a timing diagram of photocell detection andits relationship with the flip-flop 30 is illustrated. “Q” is ON (set)every time S is ON. S is triggered or ON when the leading photo sensorP1 sensors a sprocket hole 14. “Q” is OFF (reset) every time R is ON. Ris triggered or ON when the lagging photocell P2 detects a sprocket hole14. As illustrated in FIG. 11, the leading photo sensor P1 is turned ONat time t₁ when the second to last (n−1) sprocket hole 14 is reached.This sets “Q” in the ON position. “Q” is not reset until time t₂ whenthe lagging photo sensor P2 is turned ON. “Q” remains in the OFFposition until time t₄, when the photo sensor P1 is once againactivated. This occurs when the beginning of each sprocket hole isreached. Accordingly, the pair of photo sensors P1 and P2 consistentlydetect each serial sprocket hole 14 up to the nth sprocket hole for agiven pocket size. That is, it counts the sprocket holes passing thesensor.

Utilizing photo sensors P1 and P2 in this manner eliminates anypotential jitter problems that may occur.

As the carrier tape 12 is advanced the distance between sprocket holesn−1 and n, the carrier tape 12 can move (i.e. jitter) backwardsslightly, as opposed to always moving forward. In such a case, if thecarrier tape 12 is advanced to just beyond the n−1 sprocket hole 14, andjitter forces the carrier tape 12 slightly backward, either photo sensorP1 or P2 may count the n−1 sprocket twice.

However, by using the pair of photo sensors P1 and P2 in tandem asdisclosed in this invention, both the leading edge and trailing edge ofeach sprocket hole 14 must be encountered before allowing the encoder toincrement or decrement the sprocket hole 14 count. Jitter does not movethe carrier tape 12 so far back such that both photo sensors P1 and P2are activated. Accordingly, slight jitter will not increment thecounter, and therefore, the sprocket hole count of the encoder remainsaccurate.

What is claimed is:
 1. In a system for loading devices into a carriertape having a plurality of compartments of a size to receive one of saiddevices, wherein said compartments are serially spaced along thelongitudinal axis of said tape and include a first compartmentimmediately adjacent to a second compartment, wherein said tape alsoincludes a plurality of sprocket holes serially spaced along a linewhich is parallel to said longitudinal axis, and wherein said tape istransported to a placement position in which said devices are placedinto said compartments, the steps of positioning said compartments atsaid placement position in three steps, a first step positioning saidfirst compartment in said placement position, a second step positioningand substantially stopping said second compartment in the vicinity ofbut not at the placement position while simultaneously moving said firstcompartment out of said placement position and the third subsequent stepmoving said second compartment into said placement position.
 2. Thesystem of claim 1 wherein at the end of said second step said secondcompartment is located, relative to the travel of said tape to saidplacement position, upstream of said placement position.
 3. The systemof claim 1 wherein the distance between compartments corresponds to apredetermined number of sprocket holes and including the steps ofcontrolling the transport of said tape by counting the passage ofsprocket holes past a preselected area in the path of travel of saidtape, effecting the end of said second step when less than all of saidpredetermined number of sprocket holes have passed said preselectedarea, and effecting the end of said third step when all of saidpredetermined number of sprocket holes have passed said preselectedarea.
 4. The system of claim 3 wherein the predetermined number ofsprocket holes is n and the end of said second step is effected when n−1sprocket holes have passed said preselected area.
 5. The system of claim4 wherein at the end of said second step said second compartment islocated, relative to the travel of said tape to said placement position,upstream of said placement position.
 6. The system of claim 5 includingthe step of transporting said tape by engaging the tape surfaces and notthe sprocket holes.
 7. The system of claim 6 including the steps ofinspecting the orientation of a device in a compartment downstream ofsaid placement position, and in response to a device being displaced ina compartment reversing the direction travel of said tape and returningsaid tape to said placement position.
 8. The system of claim 7 includingthe steps of transporting a cover tape into overlapping relationshipwith said carrier tape downstream of said placement position, andengaging said cover tape with said carrier tape and sealing said covertape to said carrier tape to close said compartment.
 9. In a system forloading devices into a carrier tape having a plurality of compartmentsof a size to receive one of said devices, wherein said compartments areserially spaced along the longitudinal axis of said tape, wherein saidtape also includes a plurality of sprocket holes serially spaced along aline which is parallel to said longitudinal axis, and wherein said tapeis transported to a placement position in which said devices are placedinto said compartments, the steps of positioning said compartments atsaid placement position in two steps, a first step positioning one ofsaid compartments in the vicinity of but not at the placement positionand the second subsequent step moving said compartment into saidplacement position, and including the step of transporting said tape byengaging the tape surfaces and not the sprocket holes.
 10. In a systemfor loading devices into a carrier tape having a plurality ofcompartments of a size to receive one of said devices, wherein saidcompartments are serially spaced along the longitudinal axis of saidtape, wherein said tape also includes a plurality of sprocket holesserially spaced along a line which is parallel to said longitudinalaxis, and wherein said tape is transported to a placement position inwhich said devices are placed into said compartments, the steps ofpositioning said compartments at said placement position in two steps, afirst step positioning one of said compartments in the vicinity of butnot at the placement position and the second subsequent step moving saidcompartment into said placement position, wherein the distance betweencompartments corresponds to a predetermined number of sprocket holes, insaid first step said tape is advanced a distance corresponding to lessthan said predetermined number of sprocket holes, and in said secondstep said tape is advanced the remaining number of said sprocket holesto totally advance said tape the predetermined number of sprocket holes.11. The system of claim 10 including the step of counting the number ofsprocket holes advanced in said first and second steps.
 12. In a systemfor loading devices into a carrier tape having a plurality ofcompartments of a size to receive one of said devices, wherein saidcompartments are serially spaced along the longitudinal axis of saidtape, wherein said tape also includes a plurality of sprocket holesserially spaced along a line which is parallel to said longitudinalaxis, and wherein said tape is transported to a placement position inwhich said devices are placed into said compartments, the steps ofpositioning said compartments at said placement position in two steps, afirst step positioning one of said compartments in the vicinity of butnot at the placement position and the second subsequent step moving saidcompartment into said placement position, wherein said tape compartmenthas a base and upstanding side walls extending from said base to asurface of said tape and a hole is provided in said base and includingthe steps of inspecting said compartment through said hole afteroperation to place a device in said compartment, and in response to saidinspection determining that there is no device in one of saidcompartments reversing the direction of transport of said tape andreturning said one of said compartments to said placement position. 13.In a system for loading devices and including a source of carrier tapehaving a plurality of compartments of a size to receive one of saiddevices and wherein said compartments are serially spaced along thelongitudinal axis of said tape, wherein said tape includes a pluralityof sprocket holes serially spaced along a line which is parallel to saidlongitudinal axis, and including a drive for transporting said tape to aplacement position in which said devices are placed into saidcompartments, the combination comprising, a sensor positioned in thepath of movement of said sprocket holes and operatively connected to andcontrolling said drive, said sensor responding to the passage of asprocket hole and de-energizing said drive in response to the passage ofsaid sprocket holes to position one of said compartments in apredetermined location.
 14. The system of claim 13 wherein the distancebetween compartments corresponds to a predetermined number of sprocketholes, said sensor de-energizes said drive when less than thepredetermined number of sprocket holes passes said sensor, said drive isre-energized, and said sensor again de-energizes when the number ofsprocket holes remaining in said predetermined number are sensed by saidsensor.
 15. The system of claim 14 wherein said sensor includes firstand second sensing devices spaced one from the other in the direction oftravel of said tape, and said first and second sensing device respond tothe passage of, relative to direction of tape travel, a leading edge ofa sprocket hole.
 16. The system of claim 15 wherein said sprocket holesare spaced apart a distance d, and said first and second sensing devicesare spaced apart the distance d.
 17. The system of claim 16 wherein eachof first and second sensing devices each include a pair of sensingelements, one sensing element positioned on one side of said tape andthe second sensing element positioned on the other side of said tape sothat said tape sprockets pass between said pairs of sensing elements.18. A method for loading devices into a carrier tape having a pluralityof compartments of a size to receive one of the devices, the pluralityof compartments including a first compartment immediately adjacent to asecond compartment, the method comprising: positioning the firstcompartment in a placement position; positioning and substantiallystopping the second compartment in the vicinity of, but not at, theplacement position while simultaneously moving the first compartment outof the placement position; moving the second compartment into theplacement position; and placing a device in the second compartment whilethe second compartment is in the placement position.
 19. The method ofclaim 18, wherein the second compartment is located upstream of theplacement position at the end of positioning and substantially stoppingthe second compartment.
 20. The method of claim 18, wherein the carriertape includes a plurality of sprocket holes, the method furthercomprising transporting the carrier tape by engaging surfaces of thecarrier tape and not the plurality of sprocket holes.
 21. The method ofclaim 18, wherein the carrier tape includes a plurality of sprocketholes, and wherein the distance between compartments corresponds to apredetermined number of the sprocket holes; wherein positioning andsubstantially stopping the second compartment advances the carrier tapea distance corresponding to less than the predetermined number of thesprocket holes; wherein moving the second compartment into the placementposition advances the carrier tape the remaining number of the sprocketholes to totally advance the carrier tape the predetermined number ofthe sprocket holes.
 22. The method of claim 21, further comprisingcounting the number of sprocket holes advanced in positioning andsubstantially stopping the second compartment, and counting the numberof sprocket holes advanced in moving the second compartment into theplacement position.